Snow plows typically include, in addition to the moldboard, a pair of opposed generally planar wing plates fixed to opposed longitudinal ends of the moldboard. These wing plates cooperate with the moldboard in scooping snow during plowing operations. The structural stability of these wing plates, relative to the rest of the snow plow, is important because the wing plates are subject to significant stresses and could be bent or sheared away from the snow plow if not properly reinforced.
It is not uncommon for a snow plow to strike obstacles during snow clearing operations, such as frozen debris or objects buried beneath the snow such as road curbs and manhole covers. One approach to dealing with this problem is described in U.S. Pat. No. 2,962,821 to Pietl, which teaches a snow plow having individual blade sections that are oriented at a steep angle to the surface being plowed. The blade sections are slidingly received within guide pockets on the moldboard and are biased forwardly by springs, so that the blades can retract into the pockets when striking an obstacle. More typically, snow plow blades are mounted to snow plow bodies with a resilient trip mechanism that allows a snow plow blade to yield by generally pivoting upwardly and rearwardly upon striking such obstacles and to be restored to an operative position after encountering an obstacle. U.S. Pat. No. 4,794,710 to Haring, U.S. Pat. No. 5,437,113 to Jones, U.S. Pat. No. 5,697,172 to Verseef, British Patent Specification No. 886,572, German Patent Specification No. 3205974 and European Patent No. 1,557,494 provide examples of such resilient trip mechanisms.
In addition to the problem of obstacles, unevenness of the surface to be plowed also presents a problem, since a localized elevation can cause the entire snow plow to be lifted up. This leaves lower parts of the surface adjacent the elevation with a layer of snow. Similarly, the snow within a localized depression may also not be removed because the blade is carried by the higher surface adjacent the depression. A number of solutions to this issue have been proposed.
U.S. Pat. No. 4,669,205 to Smathers teaches a snow plow having a segmented blade formed from a plurality of individual bits each carried by a vertical shank of triangular cross-section which is slidably mounted in a triangular retention means on the moldboard of the snow plow, with the bits biased downwardly. The bits can be individually displaced upon encountering a higher point in the surface being plowed or an obstacle. According to this patent, “[t]he shanks to which the bits are attached must have a triangular cross-section” because “this is the only configuration which works satisfactorily”.
U.S. Pat. No. 5,743,032 teaches a snow plow in which individual blades are attached to the moldboard by flexible members which permit the individual blades to move in one direction in response to obstacles or depressions in the surface being plowed.
U.S. Pat. No. 5,819,443 teaches a snow plow comprising a frame and a plurality of finger members each comprising a plowing portion and a curved flexing portion to enable the plowing portion to remain in contact with an uneven surface.
U.S. Pat. No. 6,823,615 to Strait describes a sectional snow plow made up of several individual sections, each mounted to a frame by flexible, resilient members so as to be independently movable. The sections can each move upwardly and downwardly relative to adjacent sections of the snowplow in response to variations in the surface below that section without causing the adjacent sections to be lifted above their respective surfaces. In the commercial embodiment offered by Arctic Snow and Ice Control, each section includes a resilient trip mechanism that allows the snow plow blade to yield by generally pivoting upwardly and rearwardly. The entire plowing face is formed by the individual moldboard sections, without any single moldboard extending the entire length of the plow, and the wing plates are pivotally mounted to the snow plow frame to provide a leveling function.
It remains a challenge in snow plow design to provide a snow plow that can effectively accommodate uneven surfaces as well as obstacles. It is a particular challenge to provide such a snow plow with a wing plate structure with adequate stability. It is also desirable to provide for leveling of the snow plow, and to provide an adjustable vehicle mounting assembly for a snow plow.